The present invention relates to prefabrication of a multiphase a.c. winding for a linear motor. More particularly, the invention relates to three-phase windings for such motors, to be prefabricated for placement into the stator core of the motor as a coherent, uniform assembly.
The linear motor of the type to which the invention pertains is comprised of a long stator, cooperating with a movable armature and being comprised of a core having grooves for receiving the stator winding. It has been suggested to construct the stator windings as a coherent assembly of three cables; see, for example, U.S. Pat. No. 4,246,694 (German printed patent Application No. 27,21,905). The invention relates particularly to improvements in the prefabricated structure of such windings.
Linear motors are well known in the art. These motors are constructed as d.c. or a.c. motors, the latter being either of the asynchronous or of the synchronous type. In other words, the various dynamic principles and practices employed for and in rotary motors have been adapted to linear-motor-type structures. The stator defines, so to speak, a linear track path, and electrical energy is transmitted from that track to a mobile armature running along the track.
The stator of a linear motor is an inductor, having a core which is provided with parallel grooves; the windings are placed into the grooves, e.g., in a three-phase-type pattern. The armature may be composed of a simple, relatively short rail or section made of electrically conductive material such as copper or aluminum. This kind of armature completes an asynchronous motor. In the case of a synchronous motor, the armature is made of permanent magnetic material.
It should be noted that linear motors are known, in which the energizing coil is mounted in the armature. However, at present we are concerned only with motors, in which the stator is to be provided with windings. Broadly speaking, though, the inventive principle may be applied to any long portion, be it the armature or the stator, of a linear motor.
Linear motors can be used in many different fields of application. They can be used for transportation of people, freight, or both; for conveyors and baggage handling systems; in mining, for dredging, or in cranes. Smaller motors may be used to drive machine tool carriages or slides, or the like. By and large, the borderline between a solenoid and a linear motor is not well defined. The invention is also applicable to the former; but long, linear motor assemblies are the preferred area of application and use because simplifying the manufacture of a long stator is a rather pressing problem. It is quite clear that a long stator requires extensive installation work, in particular, the placement of the windings; and even small savings on a per-meter basis may amount to considerable overall savings.
In order to simplify installation, it has been suggested to prefabricate the windings as a coherent assembly; see German Patent Application DAS No. 27,21,905, corresponding to U.S. Pat. No. 4,246,694. In this particular assembly, emphasis is placed upon directly fastening the cable to each other. Also, covering the cable in grooves of the stator core is suggested in this reference. The particular prefabrication method as disclosed therein is, indeed, very practical because it permits, in fact, the prefabrication of long windings. However, the placing of individual cable portions and their positive positioning in the stator core grooves still requires rather extensive manipulation.